Field of the Disclosed Embodiments
The disclosed embodiments relate generally to hydraulic grips and specifically to hydraulic grips for material testing, where the grips have gripping members which are synchronized by being connected to a common link.
Background of the Disclosed Embodiments
Several companies currently manufacture various styles of synchronized power grips. Systems utilizing a pair of such grips will grip a specimen and apply tension to the specimen for the purpose of testing the stress/strain characteristics of the specimen. Notable grip manufacturers are Zwick and Demgen, both of Germany. These companies offer grips that are mechanically and hydraulically synchronized. The mechanically synchronized offerings make use of known rack and pinion gear systems for synchronizing the grips.
Systems using a rack and pinion configuration often have performance limitations related to strength and durability of the synchronization mechanism. In the presence of contamination, the rack and pinion interface is susceptible to diminished performance. The synchronizer components in a rack and pinion system are typically complicated to manufacture, assemble and adjust. This creates difficulty with maintenance and serviceability and often requires the grips to be pulled from operation and returned to the manufacturer for repair.
Systems using a rigidly coupled mechanical synchronization offer no protection from overloading. Such systems are limited to testing situations that do not produce a clamping load biased towards one half of the gripping tool, for example, when attempting to clamp a bent specimen. Without overload protection, the unequal clamping load transmitted to the synchronization mechanism can result in diminished performance and component failure.
In contrast, hydraulically synchronized systems typically lack the precision necessary to provide accurate and repeatable on center clamping. Another characteristic of hydraulic systems is the need to frequently resynchronize the system through a time consuming procedure.
In view of the stated shortcomings of known gripping mechanisms, it is an object of the disclosed embodiments to provide a design for synchronizing dual side acting specimen grips used for materials testing. The disclosed embodiments should provide precise and repeatable on center clamping, an ability to function continually in a contamination filled environment, should require minimal maintenance with field serviceability, and provide an overall robust design capable of withstanding the loads associated with high capacity materials testing.